Brucella species, members of Category B agents, are highly infectious Gram-negative bacteria that have been identified as potential biological weapons. Brucellosis is naturally transmitted via ingestion of unpasteurized dairy products, manifesting with flu-like systems and, despite antibiotic treatment, can cause a recurring sequelae, evident as undulant fever and arthritis. Brucellae survival within the host is linked to its ability to resist intracellular recognition, thus, allowing them to sequester in various tissues. To date, there are no effective vaccines for humans, but protection is cell-mediated immunity-dependent, particularly, involving TNF-? and IFN-?. Vaccines that can recapitulate such responses should prove effective in resolving Brucella infections. Two putative polyamine-binding proteins, PotD and PotF, when formulated with ISCOMs plus CpG, conferred immune protection equivalent to the live Rev-1 Brucella melitensis vaccine in mice parenterally challenged with virulent B. melitensis 16M strain. This level of protection (>4 log reduction in tissue colonization) has yet to be shown using a subunit vaccine approach. Given the potency of this vaccine formulation, we are uniquely poised to test the efficacy of these vaccines against parenteral and pulmonary B. melitensis, B. abortus, and B. suis challenges. Thus, we hypothesize that an appropriately formulated vaccine composed of PotD and PotF, combined with a suitable adjuvant for human use, will confer protection against parenteral and pulmonary Brucella challenge. Identifying polyamine-binding proteins as vaccine targets could eventually be further adapted for other Category A and B pathogens. To further this effort, studies in Specific Aim 1 will optimize the dosage and route for Brucella vaccines, PotD and PotF, to confer protection against parenteral and pulmonary B. melitensis challenges and develop correlates for protective immunity. Studies in Specific Aim 2 will optimize the dosage for adjuvant when combined with PotD and PotF to confer optimal protection against parenteral and aerosolized B. melitensis, B. abortus, and B. suis challenges. Studies in Specific Aim 3 will test the efficacy of PotD and PotF vaccines in a caprine brucellosis animal model for their ability to confer protection against mucosally challenged goats for B. melitensis colonization and abortion. Studies in Specific Aim 4 will evaluate various safety parameters for GLP- prepared PotD and PotF subunit vaccines. Thus, these studies will show that subunit vaccines, when appropriately delivered, can protect against parenteral and pulmonary Brucella challenges.